[syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    2df0c02dab82 x86 boot build: make git ignore stale 'tools'..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14e3aa4c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5f1762820c18874b
dashboard link: https://syzkaller.appspot.com/bug?extid=ab13429207fe1c8c92e8
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12985804580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1749a198580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/93b59f97f896/disk-2df0c02d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f0ade1042ab8/vmlinux-2df0c02d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7c64e746afbb/bzImage-2df0c02d.xz

The issue was bisected to:

commit e2c2cb8ef07affd9f69497ea128fa801240fdf32
Author: David Howells <dhowells@redhat.com>
Date:   Mon Feb 24 16:06:03 2025 +0000

    afs: Simplify cell record handling

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15f1e198580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=17f1e198580000
console output: https://syzkaller.appspot.com/x/log.txt?x=13f1e198580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ab13429207fe1c8c92e8@syzkaller.appspotmail.com
Fixes: e2c2cb8ef07a ("afs: Simplify cell record handling")

------------[ cut here ]------------
ODEBUG: activate active (active state 1) object: ffff888025e8e118 object type: rcu_head hint: 0x0
WARNING: CPU: 1 PID: 5839 at lib/debugobjects.c:615 debug_print_object+0x17a/0x1f0 lib/debugobjects.c:612
Modules linked in:
CPU: 1 UID: 0 PID: 5839 Comm: strace-static-x Not tainted 6.14.0-syzkaller-01103-g2df0c02dab82 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:debug_print_object+0x17a/0x1f0 lib/debugobjects.c:612
Code: e8 8b a3 2d fd 4c 8b 0b 48 c7 c7 40 24 80 8c 48 8b 74 24 08 48 89 ea 44 89 e1 4d 89 f8 ff 34 24 e8 5b 2a 87 fc 48 83 c4 08 90 <0f> 0b 90 90 ff 05 48 c6 40 0b 48 83 c4 10 5b 41 5c 41 5d 41 5e 41
RSP: 0018:ffffc90000a08838 EFLAGS: 00010282
RAX: bc12de5074ab4600 RBX: ffffffff8c2bc520 RCX: ffff88802edfda00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff8c8025c0 R08: ffffffff81826ce2 R09: fffffbfff1d3a71c
R10: dffffc0000000000 R11: fffffbfff1d3a71c R12: 0000000000000001
R13: ffffffff8c8024d8 R14: dffffc0000000000 R15: ffff888025e8e118
FS:  00000000101f03c0(0000) GS:ffff88812535a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555db2c838 CR3: 000000007bba6000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 debug_object_activate+0x350/0x5c0 lib/debugobjects.c:842
 debug_rcu_head_queue kernel/rcu/rcu.h:224 [inline]
 __call_rcu_common kernel/rcu/tree.c:3067 [inline]
 call_rcu+0x99/0xad0 kernel/rcu/tree.c:3202
 radix_tree_node_free lib/radix-tree.c:310 [inline]
 delete_node+0x1b2/0x780 lib/radix-tree.c:573
 radix_tree_delete_item+0x2e6/0x3f0 lib/radix-tree.c:1430
 afs_cell_destroy+0x175/0x2c0 fs/afs/cell.c:522
 rcu_do_batch kernel/rcu/tree.c:2568 [inline]
 rcu_core+0xaac/0x17a0 kernel/rcu/tree.c:2824
 handle_softirqs+0x2d6/0x9b0 kernel/softirq.c:561
 __do_softirq kernel/softirq.c:595 [inline]
 invoke_softirq kernel/softirq.c:435 [inline]
 __irq_exit_rcu+0xfb/0x220 kernel/softirq.c:662
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:678
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__preempt_count_add arch/x86/include/asm/preempt.h:80 [inline]
RIP: 0010:rcu_is_watching+0x9/0xb0 kernel/rcu/tree.c:735
Code: 03 eb cd 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 41 56 53 <65> ff 05 f0 cc 93 11 e8 6b 3a 6a 0a 89 c3 83 f8 08 73 7a 49 bf 00
RSP: 0018:ffffc90003fc78c8 EFLAGS: 00000202
RAX: 0000000000000000 RBX: ffff8880591cbc00 RCX: ffff88802edfda00
RDX: ffff88802edfda00 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffffff818c7bf9 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff933c6020 R14: ffffffff818c7bc8 R15: 0000000000000000
 rcu_read_lock include/linux/rcupdate.h:842 [inline]
 __task_pid_nr_ns+0x62/0x460 kernel/pid.c:518
 task_pid_vnr include/linux/pid.h:242 [inline]
 wait_task_stopped kernel/exit.c:1359 [inline]
 wait_consider_task+0x1fab/0x30e0 kernel/exit.c:1529
 ptrace_do_wait kernel/exit.c:1569 [inline]
 __do_wait+0x205/0x850 kernel/exit.c:1677
 do_wait+0x1e9/0x550 kernel/exit.c:1707
 kernel_wait4+0x2ac/0x3c0 kernel/exit.c:1866
 __do_sys_wait4 kernel/exit.c:1894 [inline]
 __se_sys_wait4 kernel/exit.c:1890 [inline]
 __x64_sys_wait4+0x136/0x1e0 kernel/exit.c:1890
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x4d6ad6
Code: 00 00 00 90 31 c9 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 49 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 90 48 83 ec 28 89 54 24 14 48 89 74 24
RSP: 002b:00007ffeafb16778 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004d6ad6
RDX: 0000000040000000 RSI: 00007ffeafb1679c RDI: 00000000ffffffff
RBP: 0000000000000000 R08: 0000000000000017 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000101f8f40
R13: 00007ffeafb1679c R14: 00000000101f28b0 R15: 000000000063f160
 </TASK>
----------------
Code disassembly (best guess):
   0:	03 eb                	add    %ebx,%ebp
   2:	cd 66                	int    $0x66
   4:	66 66 66 66 2e 0f 1f 	data16 data16 data16 cs nopw 0x0(%rax,%rax,1)
   b:	84 00 00 00 00 00
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	90                   	nop
  1c:	90                   	nop
  1d:	90                   	nop
  1e:	90                   	nop
  1f:	90                   	nop
  20:	90                   	nop
  21:	f3 0f 1e fa          	endbr64
  25:	41 57                	push   %r15
  27:	41 56                	push   %r14
  29:	53                   	push   %rbx
* 2a:	65 ff 05 f0 cc 93 11 	incl   %gs:0x1193ccf0(%rip)        # 0x1193cd21 <-- trapping instruction
  31:	e8 6b 3a 6a 0a       	call   0xa6a3aa1
  36:	89 c3                	mov    %eax,%ebx
  38:	83 f8 08             	cmp    $0x8,%eax
  3b:	73 7a                	jae    0xb7
  3d:	49                   	rex.WB
  3e:	bf                   	.byte 0xbf


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[David Howells]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

commit db7a516159869b19f237c73bd75599bbe0bfcc4d
Author: David Howells <dhowells@redhat.com>
Date:   Fri Mar 28 16:46:58 2025 +0000

    afs: Fix afs_dynroot_readdir() to not use the RCU read lock
    
    afs_dynroot_readdir() uses the RCU read lock to walk the cell list whilst
    emitting cell automount entries - but dir_emit() may write to a userspace
    buffer, thereby causing a fault to occur and waits to happen.
    
    Fix afs_dynroot_readdir() to get a shared lock on net->cells_lock instead.
    
    Fixes: 1d0b929fc070 ("afs: Change dynroot to create contents on demand")
    Reported-by: syzbot+3b6c5c6a1d0119b687a1@syzkaller.appspotmail.com
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Marc Dionne <marc.dionne@auristor.com>
    cc: linux-afs@lists.infradead.org
    cc: linux-fsdevel@vger.kernel.org

diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index 691e0ae607a1..8c6130789fde 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -348,9 +348,9 @@ static int afs_dynroot_readdir(struct file *file, struct dir_context *ctx)
 	}
 
 	if ((unsigned long long)ctx->pos <= AFS_MAX_DYNROOT_CELL_INO) {
-		rcu_read_lock();
+		down_read(&net->cells_lock);
 		ret = afs_dynroot_readdir_cells(net, ctx);
-		rcu_read_unlock();
+		up_read(&net->cells_lock);
 	}
 	return ret;
 }

Re: [syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for batadv0 to become free. Usage count = 3


Tested on:

commit:         1e7857b2 x86: don't re-generate cpufeaturemasks.h so e..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12692404580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=56c806e1bbb36dee
dashboard link: https://syzkaller.appspot.com/bug?extid=ab13429207fe1c8c92e8
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=178cce4c580000

Re: [syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[David Howells]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Re: [syzbot] [afs?] WARNING: ODEBUG bug in delete_node (3)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: ODEBUG bug in delete_node

------------[ cut here ]------------
ODEBUG: activate active (active state 0) object: ffff888148ef4dd8 object type: rcu_head hint: 0x0
WARNING: CPU: 1 PID: 6466 at lib/debugobjects.c:615 debug_print_object+0x16b/0x1e0 lib/debugobjects.c:612
Modules linked in:
CPU: 1 UID: 0 PID: 6466 Comm: syz-executor Not tainted 6.16.0-rc7-syzkaller-g89be9a83ccf1 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:debug_print_object+0x16b/0x1e0 lib/debugobjects.c:612
Code: 4c 89 ff e8 e7 83 60 fd 4d 8b 0f 48 c7 c7 80 d1 e1 8b 48 8b 34 24 4c 89 ea 89 e9 4d 89 f0 41 54 e8 3a 0d c3 fc 48 83 c4 08 90 <0f> 0b 90 90 ff 05 f7 30 de 0a 48 83 c4 08 5b 41 5c 41 5d 41 5e 41
RSP: 0018:ffffc90000a088e0 EFLAGS: 00010292
RAX: 3ffe616a0f195300 RBX: dffffc0000000000 RCX: ffff88802d3a1e00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfaa6c R12: 0000000000000000
R13: ffffffff8be1d300 R14: ffff888148ef4dd8 R15: ffffffff8b8bde80
FS:  000055556b314500(0000) GS:ffff888125da5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f26e42d56c0 CR3: 00000000342c0000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 debug_object_activate+0x26a/0x420 lib/debugobjects.c:842
 debug_rcu_head_queue kernel/rcu/rcu.h:236 [inline]
 __call_rcu_common kernel/rcu/tree.c:3079 [inline]
 call_rcu+0xaa/0x9c0 kernel/rcu/tree.c:3214
 radix_tree_node_free lib/radix-tree.c:310 [inline]
 delete_node+0x1b6/0xa50 lib/radix-tree.c:573
 radix_tree_delete_item+0x2b6/0x400 lib/radix-tree.c:1430
 afs_cell_destroy+0x16f/0x2c0 fs/afs/cell.c:522
 rcu_do_batch kernel/rcu/tree.c:2576 [inline]
 rcu_core+0xca5/0x1710 kernel/rcu/tree.c:2832
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:check_preemption_disabled+0x17/0x120 lib/smp_processor_id.c:14
Code: 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41 57 41 56 53 48 83 ec 10 65 48 8b 05 ee 4d 3b 07 48 89 44 24 08 <65> 8b 05 f6 4d 3b 07 65 8b 0d eb 4d 3b 07 f7 c1 ff ff ff 7f 74 23
RSP: 0018:ffffc90003def330 EFLAGS: 00000286
RAX: 3ffe616a0f195300 RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff88802d3a1e00 RSI: ffffffff8be1c7c0 RDI: ffffffff8be1c780
RBP: ffff88801e0ffe10 R08: ffff88801e0ffe0b R09: 1ffff11003c1ffc1
R10: dffffc0000000000 R11: ffffed1003c1ffc2 R12: ffffffff822c91ad
R13: 0000000000000001 R14: 000000000007332c R15: 0000000000000001
 rcu_is_watching_curr_cpu include/linux/context_tracking.h:128 [inline]
 rcu_is_watching+0x15/0xb0 kernel/rcu/tree.c:745
 rcu_read_unlock include/linux/rcupdate.h:869 [inline]
 page_table_check_set+0x4ad/0x730 mm/page_table_check.c:124
 page_table_check_ptes_set include/linux/page_table_check.h:76 [inline]
 set_ptes include/linux/pgtable.h:292 [inline]
 __copy_present_ptes mm/memory.c:973 [inline]
 copy_present_ptes mm/memory.c:1056 [inline]
 copy_pte_range mm/memory.c:1179 [inline]
 copy_pmd_range+0x4262/0x7000 mm/memory.c:1267
 copy_pud_range mm/memory.c:1304 [inline]
 copy_p4d_range mm/memory.c:1328 [inline]
 copy_page_range+0xc46/0x1270 mm/memory.c:1416
 dup_mmap+0xf57/0x1ac0 mm/mmap.c:1838
 dup_mm kernel/fork.c:1477 [inline]
 copy_mm+0x13c/0x4b0 kernel/fork.c:1529
 copy_process+0x16d3/0x3b80 kernel/fork.c:2169
 kernel_clone+0x224/0x7f0 kernel/fork.c:2599
 __do_sys_clone kernel/fork.c:2742 [inline]
 __se_sys_clone kernel/fork.c:2726 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2726
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f26e35839d3
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007fff070e2f88 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26e35839d3
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 000055556b3147d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 0000000000070948 R15: 00007fff070e3120
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	00 90 90 90 90 90    	add    %dl,-0x6f6f6f70(%rax)
   8:	90                   	nop
   9:	90                   	nop
   a:	90                   	nop
   b:	90                   	nop
   c:	90                   	nop
   d:	90                   	nop
   e:	90                   	nop
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	55                   	push   %rbp
  14:	41 57                	push   %r15
  16:	41 56                	push   %r14
  18:	53                   	push   %rbx
  19:	48 83 ec 10          	sub    $0x10,%rsp
  1d:	65 48 8b 05 ee 4d 3b 	mov    %gs:0x73b4dee(%rip),%rax        # 0x73b4e13
  24:	07
  25:	48 89 44 24 08       	mov    %rax,0x8(%rsp)
* 2a:	65 8b 05 f6 4d 3b 07 	mov    %gs:0x73b4df6(%rip),%eax        # 0x73b4e27 <-- trapping instruction
  31:	65 8b 0d eb 4d 3b 07 	mov    %gs:0x73b4deb(%rip),%ecx        # 0x73b4e23
  38:	f7 c1 ff ff ff 7f    	test   $0x7fffffff,%ecx
  3e:	74 23                	je     0x63


Tested on:

commit:         89be9a83 Linux 6.16-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16517722580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8ba21f95b63d6db2
dashboard link: https://syzkaller.appspot.com/bug?extid=ab13429207fe1c8c92e8
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Note: no patches were applied.